1. Field of the Invention
The present invention relates to a fuel cut device for releasing fuel gas generated within a fuel tank of an automobile or a like apparatus to the exterior of the fuel tank as well as to a structure for connecting together a plurality of the fuel cut devices.
2. Description of the Related Art
To meet needs for improved riding comfort, the shape of a fuel tank of an automobile has tended to become complicated and flat. Specifically, in recent years there has been used a fuel tank whose top surface has concave and convex portions. In such a fuel tank, air or evaporated fuel is trapped within the convex portions. Accordingly, the trapped gas must be released from the fuel tank. Each convex portion, therefore, is equipped with a fuel cut device for releasing gas from the fuel tank and for preventing fuel from flowing out from the fuel tank.
Japanese Patent Laid-Open (kokai) No. 7-293385 discloses an arrangement of a plurality of fuel cut devices on a fuel tank. FIG. 6 shows the structure for connecting together the fuel cut devices of the disclosed invention. FIG. 7 shows a fuel cut device equipped with a two-way valve and used in FIG. 6.
In FIG. 6, two fuel cut devices 62 and a single fuel cut device 64 equipped with a two-way valve (hereinafter referred to as a valved fuel cut device 64) are mounted on the top surface of a fuel tank 60. The fuel cut device 62 has a conventionally known structure. Specifically, the fuel cut device 62 includes a float valve (not shown) which, when fuel enters the fuel cut device, floats on the fuel and moves upward and downward according to fuel level. When the float valve moves downward, a fuel gas vent port is opened to permit release of fuel gas to a canister (not shown). When the float valve moves upward, the fuel gas vent port is closed to prevent fuel from flowing out therethrough.
The valved fuel cut device 64 is a combination of a mechanism of the fuel cut device 62 and a two-way valve 66 (having a known structure). The two-way valve 66 establishes bidirectional communication between the canister and the fuel tank 60 according to a pressure difference therebetween. A lower partition 68 and an upper partition 70 divide the interior space of the valved fuel cut device 64 into three chambers; namely, a lower float chamber 72, an intermediate chamber 74, and an upper two-way valve chamber 76. In the lower float chamber 72 is provided a conventionally known fuel cut valve mechanism 78 (having the same mechanism as that of the fuel cut device 62). The intermediate chamber 74 is connected to the fuel cut device 62 via a connection port 80. In the two-way valve chamber 76, the two-way valve 66 is provided. The two-way valve chamber 76 is connected to a canister via a vent port 82.
As shown in FIG. 7, the valved fuel cut device 64 is attached to the fuel tank 60 such that the connection port 80 and the vent port 82 are exposed above the fuel tank 60. Also, as shown in FIG. 6, each fuel cut device 62 has a single vent port 84 and is attached to the fuel tank 60 such that the vent port 84 is exposed above the fuel tank 60.
By means of piping 86, the vent ports 84 of the fuel cut devices 62 are connected together and to the connection port 80 of the valved fuel cut device 64. The vent port 82 of the valved fuel cut device 64 is connected to a canister (not shown) by means of a pipe 88.
In order to connect two fuel cut devices 62 to a single valved fuel cut device 64 by means of the single piping 86, the piping 86 has a single connection portion 90 (a T-shaped connection portion). When three fuel cut devices 62 are to be connected to a single valved fuel cut device 64, the piping 86 has two T-shaped connection portions or a single cruciform connection portion 90.
According to a conventional practice, as shown in FIGS. 6 and 7, the vent ports 84 of the fuel cut devices 62 and the connection port 80 and vent port 82 of the valved fuel cut device 64 are exposed above the top surface of the fuel tank 60. The piping 86 for connecting the vent ports 84 and the connection port 80 is also exposed above the top surface of the fuel tank 60.
Thus, an appropriate space must be reserved above the top surface of the fuel tank 60 in order to accommodate the portions of the fuel cut devices 62 and the portion of the valved fuel cut device 64 which project above from the fuel tank 60. As a result, the volume of the fuel tank 60 cannot be increased accordingly. Particularly, the connection port 80 and the vent port 82 of the valved fuel cut device 64 are located above the top surface of the fuel tank 60 and are arranged one above the other, with the result that the valved fuel cut device 64 projects far higher above the top surface of the fuel tank 60 than do the fuel cut devices 62.
Because of the incorporation of the two-way valve 66, the valved fuel cut device 64 has a body structure different from that of the fuel cut device 62. Accordingly, when a plurality of fuel cut devices are to be attached to the fuel tank 60, two kinds of fuel cut devices--the fuel cut device 62 and the valved fuel cut device 64--must be employed, resulting in an increase in cost as compared to a case wherein fuel cut devices of a single kind are employed.
Further, the piping for connecting a single valved fuel cut device 64 and a plurality of fuel cut devices 62 includes at least one connection portion 90. Formation of the connection portion 90 in the piping 86 involves processing such as cutting, drilling, and welding, thereby incurring processing cost.